Facilitators and barriers to circular economy implementation in the wastewater management sector using ISM and MICMAC analysis

Abstract

Abstract: Northern Europe’s wastewater utilities face unique challenges, stringent effluent limits under the revised Urban Wastewater Treatment Directive (UWWTD), cold-climate constraints, and sensitive transboundary catchments that demand advanced Circular Economy (CE) approaches. Seen through a CE lens, wastewater shifts from pollutant to resource, offering opportunities for nutrient recovery, renewable energy generation, and water reuse. This study identifies and prioritises the drivers and barriers (linkage and dependent) influencing CE adoption in the sector through a mixed-method approach. A survey of 30 experts (academia, utilities, and industry) was combined with Interpretive Structural Modelling (ISM) and Matrix of Cross Impact Multiplications Applied to Classification (MICMAC) analysis to evaluate interdependencies among 25 potential factors, of which 12 emerged as critical. The results reveal Policy and Regulations (F20), Raw Wastewater Quality/Sewerage Connectivity (F23), and Effluent Water Quality (F1) as dominant driving factors that shape all subsequent outcomes. Five technical variables nutrient recovery, energy/methane recovery, sludge management, treatment technology, and material/chemical requirement were identified as linkage factors, transmitting influence across the system. Cost and environmental aspects, such as Operation & Maintenance (O&M) costs and Greenhouse Gas (GHG) emissions, were found to be dependent outcomes rather than initiators. Unlike prior studies that treat these elements in isolation, this work systematically establishes their hierarchical relationships, providing a decision-support framework for regulators, engineers, and plant operators. The findings emphasise that regulatory alignment and source-quality management must be prioritised to unlock technical and financial gains, advancing wastewater circularity in line with Sustainable Development Goal 6 (SDG) (Clean Water and Sanitation) and SDG 12 (Responsible Consumption and Production).